Method to generate antibodies to ion channels

ABSTRACT

The present invention provides a method for generating a functionally modifying antibody to an ion channel comprising immunizing a host with a cyclic peptide comprising at least part of an extracellular sequence of said ion channel.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is the U.S. National Phase entry under 35 U.S.C. §371 of PCT International Application No. PCT/EP2010/066279, filed Oct. 27, 2010, which claims the benefit of priority under 35 U.S.C. §119(e)(1) of U.S. Provisional Application No. 61/255,202, filed Oct. 27, 2009, and under 35 U.S.C. §119(a) of British Application No. 0922435.3, filed Dec. 22, 2009, all of which are incorporated herein by reference in their entirety.

The present disclosure relates to a method of generating anti-ion channel antibodies, in particular functionally modifying antibodies, employing cyclic peptides, and use of said peptides and compositions comprising the same for immunizing a host for generating said antibodies.

Ion channels are pore-forming proteins that help establish and control cell membrane potential of all living cells by allowing the flow of ions down their electrochemical gradient. They are present in the membranes that surround all biological cells. The human genome contains more than 400 ion channel genes presenting a large diversity and play critical roles in many cellular processes such as secretion, muscular contraction and the generation and propagation of action potentials in cardiac and neuronal tissues.

Ion channels are integral membrane proteins that may adopt large molecular structures based on the assembly of several proteins. Such “multi-subunit” assemblies usually involve an arrangement of identical or homologous proteins closely packed around a water-filled pore through the plane of the membrane or lipid bilayer. The pore-forming subunit(s), usually called the α-subunit, may be associated with auxiliary subunits, either membrane bound or cytosolic, that help to control activity and cell surface expression of the ion channel protein. The X-ray structure of various ion channels was recently resolved (Doyle et al. Science 280:69 (1998); Jiang et al., Nature 423:33 (2003); Long et al., Science 309:897 (2005)) and indicate that the organization of the pore structure is largely conserved among ion channel family members. The opening and closing of the ion channel pore, referred as the gating process, may be triggered by various cellular or biochemical processes.

The largest family of ion channel proteins is composed of voltage-gated channels including e.g. sodium, calcium and potassium ion channels, transient receptor potential ion channels hyperpolarization activated ion channels, inward rectifier ion channels, two-pore domain potassium channels and voltage gated proton channels. The latter depolarize in a pH-sensitive manner.

Inward rectifier ion channels are composed of 15 official and 1 unofficial members. The family can be further subdivided into 7 subfamilies based on homology.

At the present time there are about 10 voltage-gated calcium channels that have been identified.

Transient receptor potential ion channels are subdivided into 6 subfamilies based on homology: classical (TRPC), vanilloid receptors (TRPV), melastatin (TRPM), polycystins (TRPP), mucolipins (TRPML), and ankyrin transmembrane protein 1 (TRPA).

Hyperpolarization activated ion channels are sensitive to the cyclic nucleotides cAMP and cGMP, which alter the voltage sensitivity of the channel's opening. These channels are permeable to the monovalent cations K⁺ and Na⁺. There are 4 members of this family, all of which form tetramers of six-transmembrane α-subunits. As these channels open under hyperpolarizing conditions, they function as pacemaking channels in the heart, particularly the SA node.

The voltage-gated and ligand-gated ion channels are the most prominent members of the ion channel protein family. The activity of voltage-gated ion channels (e.g. calcium, sodium and potassium channels) is controlled by changes in cell membrane potentials whereas the ligand-gated ion channels (e.g. GABA-A receptors, Acethylcholine receptors) are controlled by the binding of specific intracellular or extracellular ligands. The gating mechanism is very complex, involving various membrane, pore and cytosolic structures, and differs between classes of ion channels.

Voltage-gated ion channels, sometimes referred to voltage-sensitive ion channels, are a class of transmembrane proteins that provide a basis for cellular excitability in cardiac and neuronal tissues. These channels are activated either by cell hyper- or depolarizations and generate ion fluxes that lead to control of cell membrane potential. Voltage-gated sodium channels are generally responsible for the initiation of action potentials whereas voltage gated potassium channels mediate cell membrane repolarization. The fine tuned interplay between various voltage-gated ion channels is critical for the shaping of cardiac and neuronal action potentials.

One class of voltage-gated sodium channels comprises nine different isoforms (Na_(v)1.1-1.9) and four different sodium channel specific accessory proteins have been described (SCN1b-SCN4b). The distinct functional activities of those isoforms have been described in a variety of neuronal cell types (Llinas et al., J. Physiol. 305:197-213 (1980); Kostyuk et al., Neuroscience 6:2423-2430 (1981); Bossu et al., Neurosci. Lett. 51:241-246 (1984) 1981; Gilly et al., Nature 309:448-450 (1984); French et al., Neurosci. Lett. 56:289-294 (1985); Ikeda et al., J. Neurophysiol. 55:527-539 (1986); Jones et al., J. Physiol. 389:605-627 (1987); Alonso & Llinas, 1989; Gilly et al., J. Neurosci. 9:1362-1374 (1989)) and in skeletal muscle (Gonoi et al., J. Neurosci. 5:2559-2564 (1985); Weiss et al., Science 233:361-364 (1986)). The Na_(v)1.5 and Na_(v)1.4 channels are the major sodium channel isoforms expressed in the cardiac and muscular tissue, respectively whereas Na_(v)1.1, 1.2, 1.3, 1.6, 1.7, 1.8 and 1.9 are specifically expressed in the central and peripheral nervous system. The use of the natural occurring toxin, tetrodotoxin (TTX), allowed to establish a pharmacological classification of the sodium channel isoforms based on their affinity to the toxin. The voltage-gated sodium channels were thus classified as TTX resistant (Na_(v)1.5, 1.8, 1.9) and TTX sensitive.

Certain ion channels have been associated with modulation of pain (see for example PNAS Nov. 6, 2001. vol 98 no. 23 13373-13378 and The Journal of Neuroscience 22, 2004 24(38) 832-836). The ion channel Na_(v)1.7 is believed to have the ability to modulate pain, such as neuropathic pain and thus is a particularly interesting target for therapeutic intervention. Na_(v)1.8 and Na_(v)1.9 are also thought to have a role in the modulation of pain.

Na_(v)1.7 is a voltage-activated, tetrodotoxin-sensitive sodium channel encoded by the gene SCN9A. Both gain-of-function and loss-of-function mutations of Na_(v)1.7 result in clear pain-related abnormalities in humans.

Originally, gain-of-function mutations in SCN9A were identified by linkage analysis as the cause of erythromelalgia (or primary erythermalgia) and paroxysmal extreme pain disorder (formerly familiar rectal pain). Erythromelalgia is a rare autosomal dominant disorder associated with bouts of burning pain together with heat and redness in the extremities. The complete inability to sense pain by an otherwise healthy individual, devoid of neuropathy, is a very rare phenotype. Very recently, two studies, reported by Cox et al (2006) and by Goldberg et al (2007), describe such a phenotype mapped, as an autosomal-recessive trait, to chromosome 2q24.3, a region containing the gene SCN9A. In both studies, detailed neurological tests revealed that these people are able to distinguish sharp/dull and hot/cold stimuli but have a global absence of pain sensation. All had injuries to lips and/or tongue caused by biting themselves. All had frequent bruises and cuts, and most suffered fractures or osteomyelitis.

This data constitutes strong evidence that SCN9A channelopathy, leading to loss of function of ion channel Na_(v)1.7, is associated with insensitivity to pain, in the absence of neuropathy or of cognitive, emotional or neurological disorders, and clinically validate Na_(v)1.7 as a pain-relevant target. Furthermore, from KO studies and animal pain models, it would appear that Na_(v)1.7 plays a major role in inflammatory pain.

FIG. 1 a is a diagrammatic representation of an ion channel, such as Na_(v)1.7, which comprises four domains A, B, C and D (also referred to as domain I, II, III and IV). Each domain comprises 6 transmembrane protein helixes S1, S2, S3, S4, S5 and S6. The exact amino acid number of each transmembrane protein varies depending on the database entry employed but UniProtKB/Swiss-Prot provides the following information for Na_(v)1.7:

-   in domain A transmembrane protein S1, S2, S3, S4, S5 and S6 are     assigned amino acids 122-145, 154-173, 187-205, 212-231, 248-271 and     379-404, respectively; -   in domain B transmembrane protein S1, S2, S3, S4, S5 and S6 are     assigned amino acids 739-763, 775-798, 807-826, 833-852, 869-889 and     943-968 respectively; -   in domain C transmembrane protein S1, S2, S3, S4, S5 and S6 are     assigned amino acids 1188-1211, 1225-1250, 1257-1278, 1283-1304,     1324-1351 and 1431-1457 respectively; and -   in domain D transmembrane protein S1, S2, S3, S4, S5 and S6 are     assigned amino acids 1511-1534, 1546-1569, 1576-1599, 1610-1631,     1647-1669 and 1736-1760, respectively. -   There are a number of natural variations of the sequence that are     available in public databases, for example see UniProtKB/Swiss-Prot     Q15858.

In the present disclosure S1, S2, S3, S4, S5 and S6 refers to the entities described above or a entity corresponding to same in an alternative ion channel, including wherein a different amino acid assignment is given to the same and including the corresponding entity in natural or non-natural variants and different isotypes of the same.

Each domain also contains extra-cellular hydrophilic loops E1, E2 and E3. The amino acid sequence of E1 in each domain starts after the transmembrane region S1 and ends at S2. E1 in each domain is distinct from E1 in other domains. The amino acid sequence of E2 in each domain starts after the transmembrane region S3 and ends at S4. E2 in each domain is distinct from E2 in other domains. The amino acid sequence of E3 in each domain starts after the transmembrane region S5 and ends at S6. E3 in each domain is also distinct from E3 in other domains.

Whilst the Na_(v) and Ca_(v) ion channels comprise four domains, A, B, C and D, each containing six transmembrane protein helixes, other ion channels, such as K_(v) ion channels, HCN ion channels and TRP ion channels comprise one domain. As for each domain in the Na_(v) and Ca_(v) ion channels, the K_(v) ion channels, HCN ion channels and TRP ion channels comprise 6 transmembrane protein helixes S1, S2, S3, S4, S5 and S6 and three extra-cellular hydrophilic loops E1, E2 and E3 as described above.

In a Na_(v)1.7 ion channel, the extracellular loops (E loops) are the following amino acid residues of SEQ ID NO:69 in FIG. 1 c:

Na_(v)1.7 Domain E1 amino acids E2 amino acids E3 amino acids A 146-153 206-211 272-378 B 764-774 827-832 890-942 C 1212-1224 1279-1282 1352-1430 D 1535-1545 1600-1609 1670-1735

The extracellular loops in some domains of Na_(v)1.7 share similarities with extracellular loops found in other ion channels.

Na_(v)1.7 is expressed in the peripheral nervous system i.e. in nociceptive dorsal root ganglions (DRG), most notably in nociceptive small-diameter DRG neurons, with little representation in the brain. Na_(v)1.7 distribution (e.g. sensory ending) and physiology predispose it to a major role in transmitting painful stimuli.

The expression of Na_(v)1.7 in the peripheral nervous system makes it a very attractive target for the generation of function blocking antibodies which represent an innovative approach for valuable treatment for pain with no side-effects or minimizing side effects to a tolerable level.

Neuropathic pain is a highly prevalent condition. In the United States, it is estimated to affect between 0.6 and 1.5% of the population, or 1.8 to 4.5 million people. (Pullar and Palmer, 2003). At least 1.4 million people each year are diagnosed with painful diabetic neuropathy (PDN), post-herpetic neuropathy (PHN) or trigeminal neuralgia (TN)—three major causes of neuropathic pain. Other causes of neuropathic pain include spinal cord injuries, multiple sclerosis, phantom limb pain, post-stroke pain and HIV-associated pain. If patients with neuropathic-related chronic back pain, osteoarthritis and cancer were included, the total number would at least double. Nonsteroidal anti-inflammatory drugs (NSAIDs) although frequently used, are not very effective in the treatment of neuropathic pain. Moreover, their chronic use may lead to serious gastric damage. On the other hand, the use of opioids (morphine and derivatives) is restricted to the most severe form of neuropathic pain, i.e., cancer-related neuropathy, because serious side-effects are associated with chronic treatment, such as nausea, emesis, respiratory depression, constipation and tolerance, and the potential for addiction and abuse. The latter have prevented the use of opioids in other neuropathies (Dellemijn, 1999; Namaka et al., 2004). Anti-epileptic drugs (AEDs) are known to attenuate abnormal neural hyperexcitability in the brain. In view of neural hyperexcitability playing a crucial role in neuropathic pain, it is understandable that AEDs were aimed at the treatment of chronic neuropathic pain (Renfrey, Downton and Featherstone, 2003). The most recent and important examples are gabapentin (Neurontin) and pregabalin (Lyrica, Frampton and Scott, 2004). However, even gabapentin, the gold standard for the treatment of neuropathic pain, reduces pain at best by 50% in about 40% of patients (Dworkin, 2002). Further, in contrast to opioids, gabapentin is not used in the treatment of cancer-related neuropathic pain.

As stated above, Na_(v)1.7 ‘loss of function’ mutation in human leads to insensitivity to pain (Cox et al., 2006). Moreover, Na_(v)1.7 ‘gain of function’ mutation in human leads to the pain phenotypes erythromelalgia and paroxysmal extreme pain disorder (Dib-Hajj, Yang, Waxman, 2008). Additionally, a peripherally acting small molecule blocking Na_(v)1.7 reverses hyperalgesia and allodynia in rat models of inflammatory and neuropathic pain (McGowan et al., 2009). Therefore a peripherally acting Na_(v)1.7 blocking antibody should be beneficial for pain therapy.

To date potent chemical inhibitors of ion channels have been identified but generally these are characterised by a poor selectivity against other ion channel isoforms. Given the ubiquitous distribution of ion channels in living organisms these non-selective inhibitors have been of limited utility.

It is clear from the discussion above that ion channels represent therapeutic targets of significant interest. It would be useful to have optimized techniques for generating therapeutic antibodies to these targets.

The present inventors have now found that anti-ion channel antibodies, for example functionally modifying antibodies, can be readily prepared even using short peptide sequence by employing peptides in a cyclised form for immunization.

SUMMARY OF THE INVENTION

Thus in one aspect the invention provides a method for generating a functionally modifying antibody to an ion channel comprising immunizing a host with a cyclic peptide comprising an extracellular sequence of said ion channel.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 a shows a diagrammatic representation of Nav1.7.

FIG. 1 b shows the amino acid sequence for domain A (SEQ ID NO: 65), B (SEQ ID NO: 66), C (SEQ ID NO: 67) and D (SEQ ID NO: 68) of Na_(v)1.7

FIG. 1 c shows the full amino acid sequence of Nav1.7 (SEQ ID NO: 69)

FIG. 2 shows the functional effects of certain monoclonal antibodies on human Na_(v)1.7 current in HEK cells.

FIG. 3 a shows that the 932 and 983 anti-Na_(v)1.7 monoclonal antibodies reduce electrically induced DRG spike frequency in vitro.

FIG. 3 b shows that anti-Na_(v)1.7 monoclonal antibody 932 reduces electrically induced DRG spike frequency in vitro.

FIG. 3 c shows that anti-Na_(v)1.7 monoclonal antibody 983 reduces electrically induced DRG spike frequency in vitro

FIG. 3 d shows that anti-Na_(v)1.7 monoclonal antibody 1080 reduces electrically induced DRG spike frequency in vitro

FIG. 3 e (a) shows automated Patch Clamp analysis of recombinant human Nav1.7 channels expressed in HEK cells. 983 monoclonal antibody produces a dose-dependent inhibition of Nav1.7 currents.

FIG. 3 e (b) shows automated Patch Clamp analysis of recombinant human Nav1.7 channels expressed in HEK cells. 1080 monoclonal antibody produces a dose-dependent inhibition of Nav1.7 currents.

FIG. 3 f shows automated Patch Clamp analysis of recombinant rat Nav1.7 channels expressed in HEK cells. 983 monoclonal antibody produces a dose-dependent inhibition of Nav1.7 currents. 1080 monoclonal antibody produces a ˜26% inhibition of Nav1.7 currents at 25 μg/ml.

FIG. 3 g Kinetics of human Nav1.7 inhibition by 983 monoclonal antibody.

FIG. 4 shows ELISA data for antibody 983 specific binding to Nav 1.7 peptide

FIG. 5 shows ELISA data for antibody 1080 specific binding to Nav 1.7 peptide.

FIGS. 6 to 11 show various antibody sequences.

FIG. 12 shows binding data for various polyclonal antibodies.

Surprisingly, relatively short peptides from ion channels are immunogenic in hosts when they are cyclised. In one embodiment the peptide comprises between 5 and 30, for example 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29 or 30 amino acids.

An extracellular sequence of an ion-channel as employed herein is at least for four, such as five or more consecutive tandem amino acids from an extracellular loop or region of the relevant ion channel.

In one aspect the anti-ion channel antibody is specific.

Specific as employed herein is intended to refer to the fact that the antibody is selective for the ion channel to which it is specific and can distinguish it from other ion channels and proteins, for example other ion channels in the same family. A selective antibody is one that, for example can be used to affinity purify the relevant ion channel including from other ion channels.

In one example, suitable peptides for use in the present invention may be designed by comparing the amino acid sequence of the selected ion channel to other family members to identify unique residues specific for the given ion channel of interest. Particular regions of interest such as the extracellular domains may be used in such a comparison. Cyclic peptides can then be designed based on the unique residues identified. Preferably the cyclic peptide contains at least one unique residue for the ion channel of interest. In this context unique refers to an amino acid residue which is specific for the ion channel of interest when the amino acid sequence of that ion channel is compared to at least one other, preferably all other family members for which sequences are available. In one embodiment the cyclic peptide contains two unique residues. In one embodiment the cyclic peptide contains three or four or five or six or seven or eight or nine or ten or eleven or twelve unique residues.

If a cross-reactive antibody is desired ie. an antibody which binds to more than one ion channel peptides may be designed which contain residues specific to the two or more selected ion channels, again by comparison to other family members.

If desired, Kyte Doolittle plots may be used to support the choice of peptide used. By employing a Kyte Doolittle plot it is possible to determine which peptides will comprise the highest number of the most hydrophilic residues i.e. those which are more likely to be solvent exposed.

In one example the unique residue(s) are away from the site of conjugation.

In one example unique residues for Nav1.7 are identified by amino acid sequence alignment with other available family members, i.e Nav1.1, Nav 1.2, Nav 1.3, Nav 1.4, Nav 1.5, Nav 1.6, Nav 1.8 and Nav 1.9.

The following Nav1.7 residues are unique to Nav1.7 compared to other family members i.e Nav1.1, Nav 1.2, Nav 1.3, Nav 1.4, Nav 1.5, Nav 1.6, Nav 1.8 and Nav 1.9: N146, F276, S279, L280, E281, L286, M290, N291, T292, L293, S295, E296, D298, F299, R300, K301, F317, T319, T329, I333, K773, R1218, I1224, S1357, P1360, A1361, Q1363, P1365, R1367, F1371, S1377, N1379, L1385, T1409, I1410, V1419, K1423, K1536, E1537, G1538, H1542, E1545, T1601, D1673, N1676, K1718 and E1727. Accordingly, a suitable peptide of Nav1.7 for use in the present invention comprises at least one of the following residues in the peptide sequence: N146, F276, S279, L280, E281, L286, M290, N291, T292, L293, S295, E296, D298, F299, R300, K301, F317, T319, T329, I333, K773, R1218, I1224, S1357, P1360, A1361, Q1363, P1365, R1367, F1371, S1377, N1379, L1385, T1409, I1410, V1419, K1423, K1536, E1537, G1538, H1542, E1545, T1601, D1673, N1676, K1718 and E1727.

A cyclic peptide as employed herein is a peptide where a sequence of amino acids are joined by a bond, such as a disulfide bond or amide bond, thereby forming a loop or circle with no discernable start and/or finish. The cyclic peptide may be formed from a corresponding linear peptide by various means such as, but not limited to, the following: C-terminal carboxyl group ligation to the N-terminal alpha amino group to form a peptide bond; alternatively side chain carboxyl groups (of aspartic or glutamic acid residues) may be ligated to the side chain amino group of lysine or the N-terminal alpha amino group or the C-terminal carboxyl group may be ligated to the side chain amino group of lysine; disulphide bond formation between side chains thiols of two cysteine residue separated from each other by at least three residues in the linear sequence. It may be desirable to form the “ring completing bond” in an area of overlap in the linear sequence. Area of overlap as employed herein is intended to refer to where there is a repeat of two or more amino acids occurring in the sequence. Thus a sequence of overlap as employed herein is intended to refer to where there is some commonality in the sequence, for example at least two, such as 3 or 4 amino acids are located in the same order in the sequence in two separate locations. These regions of overlap can be aligned and ligated such that an amino acid in one location replaces the corresponding amino acid in the second location to form the cyclised peptide.

Thus in one embodiment the peptide is cyclised by forming an amide bond.

In one embodiment the peptide is cyclised by forming a disulfide bond.

In one embodiment the sequence is ligated in a region of overlap in the linear sequence.

Cyclic peptides may be synthesized using any suitable method known in the art. In one embodiment the cyclic peptide is synthesized using protecting groups to prevent reactions of the amino acid side chains (Barlos, K.; Gatos, D.; Kutsogianni, S.; Papaphotiou, G.; Poulos, C.; Tsegenidis, T. Int. J. Pept. Protein Res. 1991, Vol 38, Issue 6 p 562-568) followed by cyclization and removal of the protecting groups (Kessler H et al., 1989, Computer Aided Drug Design, p 461-484; Dekker M et al, 1990, J. Peptide Research, 35, p 287-300; Gurrath M. et al., 1992, Eur. J. Biochem., 210, 911-921; Izumiya N. et al., 1981, Biopolymers, 20, 1785-1791; Brady S. F. et al., 1983, in Peptides, Structure and Function, Proceedings of the Eighth American Peptide Symposium, Ed. V. J. Hruby and D. H. Rick, pp. 127-130, Pierce Chemical Company, Rockford, Ill.; He J. X. et al., 1994, Lett. Peptide Sci., 1, 25-30).

In one embodiment the cyclic peptide employed for immunization is derived from the amino acid sequence of an E1 region, an E2 region, an E3 region or a combination thereof.

In one embodiment, wherein the ion channel comprises A, B, C and D domains such as in the sodium ion channels Na_(v) 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8 and 1.9, the cyclic peptide employed for immunization is derived from the sequence of the domain A (also referred to as I), domain B (also referred to as II), domain C (also referred to III), domain D (also referred to as IV) or a combination thereof.

In one embodiment the ion channel against which antibodies are raised is a sodium ion channel, for example Na_(v) 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8 or 1.9. The cyclic peptide employed for immunization may comprise at least part of an extracellular sequence of the ion channel wherein the extracellular sequence is the E1 region, E2 region or E3 region and may be derived from the A domain, B domain, C domain or D domain of the ion channel. In a preferred embodiment the cyclic peptide comprises at least a part of an E1 or E3 extracellular region derived from the A domain, B domain, C domain or D domain of the ion channel. In a further preferred embodiment the cyclic peptide comprises at least a part of an E1 or E3 extracellular region derived from the A domain or the B domain of the ion channel. Preferably the cyclic peptide comprises at least a part of the AE3 extracellular region or the BE1 extracellular region.

In one embodiment the ion channel against which antibodies are raised is one with a function in the modulation of pain. Ion channels thought to be involved and/or associated with modulation of pain include but are not limited to Na_(v) 1.3, Na_(v) 1.6, Na_(v) 1.7, Na_(v) 1.8, Na_(v) 1.9, Ca_(v) 3.1, Ca_(v) 3.2, Ca_(v) 3.3, Ca_(v) 2.1, Ca_(v) 2.2, Ca_(v) 2.3, K_(v) 2.1, K_(v) 2.2, K_(v) 7.x, HCN1, HCN2, TRPV1, TRPA1, ASIC1, TRPM8, TRPV3 and TRP4.

In one embodiment the ion channel against which antibodies are raised is a sodium channel, for Na_(v)1.7, Na_(v)1.8 or Na_(v)1.9, such as a Na_(v)1.7.

In one embodiment the ion channel against which antibodies are raised is a potassium ion channel K_(v) 2.1, K_(v) 2.2 or K_(v) 7.x.

In one embodiment the ion channel against which antibodies are raised is a calcium ion channel, for example Ca_(v) 3.1, Ca_(v) 3.2, Ca_(v) 3.3, Ca_(v) 2.1, Ca_(v) 2.2 or Ca_(v) 2.3.

In one embodiment the ion channel against which antibodies are raised is a hyperpolarisable channel HCN1 or HCN2.

In one embodiment the ion channel against which antibodies are raised is a non-gated ion channel, for example TRPV1, TRPA1, ASIC1, TRPM8, TRPV3 or TRP4.

In one embodiment the ion channel against which antibodies are raised is a potassium channel, for example K_(v)3.1 or 3.2.

Na_(v)1.7

In one embodiment the cyclic peptide comprises 5 or more consecutive amino acid residues from one or more of the following Na_(v) 1.7 sequences, wherein the domain A, B, C or D and the extracellular loop E1, E2 or E3, from which the peptide is derived is denoted in brackets:

(SEQ ID NO: 71) TMNNPP (AE1) (SEQ ID NO: 72) CFRNSLENNETLESIMNTLESEEDFRKY, (AE3) (SEQ ID NO: 73) EGSKDA, (AE3) (SEQ ID NO: 74) GFSTDSGQ, (AE3) (SEQ ID NO: 75) HPMTEEFKN, (BE1) (SEQ ID NO: 76) NDDCTLP, (BE3) (SEQ ID NO: 77) IERKKTIKI, (CE1) (SEQ ID NO: 78) CINTTDGSRFPASQVP, (CE3) (SEQ ID NO: 79) NRSECFALM, (CE3) (SEQ ID NO: 80) NVSQNVR, (CE3) (SEQ ID NO: 81) SVNVDKQP, (CE3) (SEQ ID NO: 82) EKEGQSQHMTE, (DE1) (SEQ ID NO: 83) KKEDGIND, (DE3) and/or (SEQ ID NO: 84) CDPKKVHP. (DE3)

In one embodiment the cyclised peptide contains a single cysteine residue linking the N-terminal to the C-terminal. For example is selected from the following sequences, wherein the domain A, B, C or D and the extracellular loop E1, E2 or E3, from which the peptide is derived is denoted in brackets. The cysteines which are underlined in selected peptides are non-naturally occurring cysteine residues in the ion channel. The naturally occurring or non-naturally occurring cysteine residues in the following peptides may be used to attach a carrier protein.

(SEQ ID NO: 85) CTMNNPP, (AE1) (SEQ ID NO: 86) CFRNSLENN, (AE3) (SEQ ID NO: 87) CTLESIMNTLESEEDFRKY, (AE3) (SEQ ID NO: 88) CEGSKDA, (AE3) (SEQ ID NO: 89) CFSTDSGQ (AE3) (SEQ ID NO: 90) CPMTEEFKN, (BE1) (SEQ ID NO: 91) DDCTLPRWHMN, (BE3) (SEQ ID NO: 92) CIERKKTIKI, (CE1) (SEQ ID NO: 78) CINTTDGSRFPASQVP, (CE3) (SEQ ID NO: 79) NRSECFALM, (CE3) (SEQ ID NO: 93) CNVSQNVR, (CE3) (SEQ ID NO: 94) VNVDKQPC (CE3) (SEQ ID NO: 95) CEKEGQSQHMTE, (DE1) and/or (SEQ ID NO: 96) KKEDGINDC. (DE3)

Other Na_(v)1.7 cyclic peptides suitable for use in generating function modifying antibodies to the extracellular domains of the stated ion channels are listed below, wherein the domain A, B, C or D and the extracellular loop E1, E2 or E3, from which the peptide is derived is denoted for each peptide before the sequence and wherein the cys* or homocys* in each peptide denotes that the cysteine or homocysteine may be coupled to a macromolecular carrier, such as a carrier protein, via maleimide chemistry:

(SEQ ID NO: 97) AE1.1 cyclic[cys*TMNNPPDW] (SEQ ID NO: 90) BE1.1 cyclic[cys*PMTEEFKN] (SEQ ID NO: 98) BE1.2 cyclic[cys*EHHPMTEEFKN] (SEQ ID NO: 92) CE1.1 cyclic[cys*IERKKTIKI] (SEQ ID NO: 95) DE1.1 cyclic[cys*EKEGQSQHMTE] (SEQ ID NO: 99) DE1.2 cyclic[homocys*GQSQH] or cyclic[cys*GQSQH] (SEQ ID NO: 100) AE3.1 cyclic[cys*FRNSLENNET] (SEQ ID NO: 87) AE3.2 cyclic[cys*TLESIMNTLESEEDFRKY] (SEQ ID NO: 89) AE3.3 cyclic[cys*FSTDSGQ] (SEQ ID NO: 88) AE3.4 cyclic[cys*EGSKDA] (SEQ ID NO: 101) BE3.1 cyclic[cys*KINDD] (SEQ ID NO: 102) BE3.2 cyclic[cys*TLPRWHMNDD] (SEQ ID NO: 103) CE3.1 cyclic[cys*INTTDGSRFPASQVPNRSE] (SEQ ID NO: 93) CE3.2 cyclic[cys*NVSQNVR] (SEQ ID NO: 94) CE3.3 cyclic[cys*VNVDKQP] (SEQ ID NO: 96) DE3.1 cyclic[homocys*KKEDGIND] or cyclic[cys*KKEDGIND] (SEQ ID NO: 84) DE3.2 cyclic[cys*DPKKVHP]

In one embodiment of the present invention the cyclic peptide has an amino acid sequence selected from the group consisting SEQ ID NOs: 71 to 103. In a preferred embodiment, the cyclic peptide has an amino acid sequence selected from the group consisting of SEQ ID NO: 87, SEQ ID NO: 90, SEQ ID NO: 92 and SEQ ID NO: 102.

K_(v)3.2

In one embodiment there is provided the following cyclic peptides useful in generating anti-K_(v)3.2 antibodies:

(SEQ ID NO: 104) CKNKTEPVINGTSPVLQYEIETD (SEQ ID NO: 105) CRVGAQPNDPSASEHTQ

Other cyclic peptides suitable for use in generating function modifying antibodies to the extracellular domains of the ion channels Na_(v)1.3, Na_(v)1.8 and Na_(v)1.9 are listed below, wherein the domain A, B, C or D and the extracellular loop E1, E2 or E3, from which the peptide is derived is denoted for each peptide before the sequence and wherein the cys* or homocys* in each peptide denotes that the cysteine or homocysteine may be coupled to a macromolecular carrier, such as a carrier protein, via maleimide chemistry:

Nav1.3

(SEQ ID NO: 106) AE1.1 cyclic[cys*TLSNPP] (SEQ ID NO: 107) DE1.1 cyclic[homocys*TDDQGKY] or cyclic[cys*TDDQGKY] (SEQ ID NO: 108) AE3.1 cyclic[cys*DSAFETNTT] (SEQ ID NO: 109) AE3.2 cyclic[cys*TMSTFNWKD] (SEQ ID NO: 110) BE3.1 cyclic[cys*KINDD] N.B. cross reactive with Nav1.7 (SEQ ID NO: 111) CE3.1 cyclic[cys*VNMTTGNMFDISD] (SEQ ID NO: 112) CE3.2 cyclic[cys*QALGKQAR] (SEQ ID NO: 113) CE3.3 cyclic[cys*RDVKLQP]

Accordingly, in one embodiment of the present invention the ion channel is Na_(v)1.3 and the cyclic peptide has an amino acid sequence selected from the group consisting of SEQ ID NOs: 106 to 113.

Nav1.8

(SEQ ID NO: 114) AE1.1 cyclic[cys*MTRTDLPEK] (SEQ ID NO: 115) BE1.1 cyclic[cys*GMSPTFEA] (SEQ ID NO: 116) BE1.2 cyclic[cys*PMTDAFDA] (SEQ ID NO: 117) BE1.3 cyclic[homocys*MEHHGMSPTFEA] or cyclic[cys*MEHHGMSPTFEA] (SEQ ID NO: 118) BE1.4 cyclic[cys*MEHYPMTDAFDA] (SEQ ID NO: 119) CE1.1 cyclic[cys*DQKPTVK] (SEQ ID NO: 120) CE1.2 cyclic[cys*EEKPRVK] (SEQ ID NO: 121) DE1.1 cyclic[cys*QSEEKTK] (SEQ ID NO: 122) DE1.2 cyclic[cys*DDQSEEK] (SEQ ID NO: 123) DE1.3 cyclic[cys*DNQSEEK] (SEQ ID NO: 124) AE3.1 cyclic[cys*VKNDMAVNK] (SEQ ID NO: 125) AE3.2 cyclic[cys*IKNGTDPHK] (SEQ ID NO: 126) AE3.3 cyclic[cys*TNYSSHRK] (SEQ ID NO: 127) AE3.4 cyclic[cys*DNLSSEMA] (SEQ ID NO: 128) BE3.1 cyclic[cys*APHEDWPR] (SEQ ID NO: 129) BE3.2 cyclic[cys*VWNGERLR] (SEQ ID NO: 130) CE3.1 cyclic[cys*INYTDGEFS] (SEQ ID NO: 131) CE3.2 cyclic[cys*VDTRSNPFS] (SEQ ID NO: 132) CE3.3 cyclic[cys*KIQNSTGS] (SEQ ID  NO: 133) CE3.4 cyclic[cys*YNQNNTGH]

Accordingly in one embodiment of the present invention the ion channel is Na_(v)1.8 and the cyclic peptide has an amino acid sequence selected from the group consisting of SEQ ID NOs: 114 to 133.

Nav1.9

(SEQ ID NO: 134) AE1.1 cyclic[cys*TGPAKNSNSNN] (SEQ ID NO: 135) AE1.2 cyclic[homocys*ATGPAKNSNSNNTD] or cyclic[cys*ATGPAKNSNSNNTD] (SEQ ID NO: 136) BE1.1 cyclic[cys*EASFEK] (SEQ ID NO: 137) BE1.2 cyclic[cys*EHHKMEASFEK] (SEQ ID NO: 138) CE1.1 cyclic[cys*ENQPKIQE] (SEQ ID NO: 139) DE1.1 cyclic[cys*ESYNQPKAMKS] (SEQ ID NO: 140) DE1.2 cyclic[cys*YNQPKAMK] (SEQ ID NO: 141) AE3.1 cyclic[cys*KNISNPEAYDH] (SEQ ID NO: 142) AE3.2 cyclic[cys*FEKKENSPEFKM] (SEQ ID NO: 143) AE3.3 cyclic[cys*GIWMGNSA] (SEQ ID NO: 144) AE3.4 cyclic[cys*SIQYE] (SEQ ID NO: 145) AE3.5 cyclic[cys*KHTKIN] (SEQ ID NO: 146) BE3.1 cyclic[cys*NSQKSPKL] (SEQ ID NO: 147) BE3.2 cyclic[cys*NPTGPTVS] (SEQ ID NO: 148) CE3.1 cyclic[cys*INGTD] (SEQ ID NO: 149) CE3.2 cyclic[cys*NKSQ] (SEQ ID NO: 150) CE3.3 cyclic[cys*ESGNFS] (SEQ ID NO: 151) CE3.4 cyclic[cys*TEKEQQPEFE] (SEQ ID NO: 152) DE3.1 cyclic[cys*NSSSKES]

Accordingly, in one embodiment of the present invention the ion channel is Na_(v)1.9 and the cyclic peptide has an amino acid sequence selected from the group consisting of SEQ ID NOs: 134 to 152.

HCN1 and HCN2

In one embodiment of the present invention the ion channel is HCN1 or HCN2 and the cyclic peptide has an amino acid sequence selected from the group consisting of SEQ ID NOs: 153 to 158 as follows, wherein the extracellular loop E1, E2 or E3, from which the peptide is derived is denoted for each peptide before each sequence and wherein the cys* or homocys* in each peptide denotes that the cysteine or homocysteine may be coupled to a macromolecular carrier, such as a carrier protein, via maleimide chemistry:

(SEQ ID NO: 153) HCN1E1.1 cyclic[cys*TEQTTT] (SEQ ID NO: 154) HCN1E3.1 cyclic[cys*QDFPPD] (SEQ ID NO: 155) HCN1E3.2 cyclic[cys*LNEMVND] (SEQ ID NO: 156) HCN2E1.1 cyclic[cys*KDETTA] (SEQ ID NO: 157) HCN2E3.1 cyclic[cys*QDFPRN] (SEQ ID NO: 158) HCN2E3.2 cyclic[cys*INGMVNH]

In one embodiment a mixture of peptide antigens from one or more (such as one) ion channel(s) are employed for immunizing a host.

In one embodiment the cyclic peptide is designed to contain a single unique functional group for covalent attachment to a macromolecular carrier such as a xenogenic protein. The single unique functional group may be a cysteine, aspartate, glutamate or lysine residue. The unique functional group may be incorporated by an additional residue (either natural or non-natural amino acid) e.g. a cysteine, to allow specific coupling.

In one embodiment a biotin linker and carrier proteins may be attached via cysteine side chain.

To prepare immunogens for the purpose of raising anti-ion channel antibodies in a host animal each peptide requires covalent conjugation to a carrier protein. The carrier protein is selected on the basis of its ‘foreigners’ to the host species; thus for immunization of rabbits or rodents examples of suitable carrier proteins are keyhole limpet hemocyanin (KLH), ovalbumin (OVA) and bovine serum albumun (BSA). Each of the above peptides, may be conjugated through the cysteine thiol to one of each of the above proteins, where the lysine side chain amino groups of the latter have been covalently modified with a maleimide functionality to yield respectively:

-   KLH-maleimide, -   Ovalbumin-maleimide, or -   BSA-maleimide.

The present disclosure explicitly envisages each one of the peptides described herein in separate conjugations with each one of the carriers listed above, thus in the case of Na_(v)1.7, 99 different molecules are specifically provided for immunizing a host to provide function modifying anti-Nav1.7 antibodies, for example KLH-CEKEGQSQHMTE (cyclic) (SEQ ID NO: 95) or BSA-CEKEGQSQHMTE (cyclic) (SEQ ID NO: 95). Accordingly, any of the cyclic peptides having an amino acid sequence selected from SEQ ID NOs: 71 to 158 may be conjugated with each of the carrier proteins listed above.

As described above, the carrier protein may be conjugated through a unique functional group such as a cysteine residue. However, any alternative naturally occurring or non-naturally occurring residue may be used in place of a cysteine residue in order to conjugate the cyclic peptide to the carrier protein. An example of a non-naturally occurring residue which may be used in place of cysteine is a homocysteine residue, which is a homologue of cysteine which further comprises an additional methylene group in the side chain. Accordingly, any of the cyclic peptides having an amino acid sequence selected from SEQ ID NOs: 71 to 158, which comprise a cysteine residue may be modified to replace the cysteine residue with an alternative suitable naturally occurring or non-naturally occurring residue for conjugation to the carrier protein, such as a homocysteine residue.

The present disclosure also extends to novel peptides disclosed herein and compositions comprising same.

Generally between 0.001 and 1 mg of each peptide-carrier protein are required for each immunization dose per host animal.

Alternative immunogens suitable for raising function modifying antibodies include: full length human ion channels, truncations thereof including individual sub-domains and truncations of sub-domains; chimeric molecules with regions of ion channel fused to regions other transmembrane proteins to aid expression or present extracellular loops to the immune system and mutations of ion channels to constrain regions of the ion channel in a desired conformation.

These immunogens may be expressed in mammalian cells for direct cell immunization or purification of protein for immunization.

These immunogens may be expressed in E. coli or cell-free expression systems for purification of protein for immunization.

Purified protein may be integrated into lipid vesicles for immunisation.

These ion channel versions may also be generated as lipoparticles for immunization.

Thus in one aspect there is provided a method of generating antibodies in a host by immunizing, for example with at least one ion channel cyclic peptide-carrier protein conjugate or several different peptides (wherein at least one is cyclic) conjugated separately or as a mixture conjugated to the same carrier protein.

In one embodiment the method involves one, two, three, four or five immunizations.

In one embodiment the method involves at least two, such as two or three immunizations with the respective conjugates peptide(s).

In one embodiment the second immunization employs a different conjugate, wherein the peptide(s) is (are) common but the carrier protein is different to the carrier protein employed in the first immunization.

Thus in one embodiment the third immunization employs a different conjugate wherein the peptide(s) is (are) common to that of the first and second immunization, but the carrier protein is different to that employed in the first and/or second immunization. Unwanted antibody specificities against the carrier protein may in this way be minimized.

Suitable carrier protein combinations for sequential immunization include, KLH and Ovalbumin and BSA in any order.

Varying the carrier may be advantageous in optimizing the response to the peptide.

Each immunization will generally also include the administration of an adjuvant to stimulate immune responses. Suitable adjuvants include Freud's complete or incomplete adjuvant, and adjuvants comprising, alum, QS21, MPL and/or CPG.

The method may further comprise a step of separating antibodies or antibody producing cells from the host.

In one embodiment the host is a mouse, rat, shark, rabbit, pig, hamster, camel, llama, goat or human, in particular a rabbit.

Generally a adjuvant is administered as part of immunizing the host to stimulate the immune response to the peptide antigen.

Suitable adjuvants are well known to those in the art and include Freud's complete or incomplete adjuvant. Compositions comprising a saponin, for example such as QS21 and/or a MPL and/or CPG may also be suitable for use as adjuvants, see for example WO00/062800.

Combinations of MPL and alum may also be employed.

The adjuvant may be administered concomitantly with the antigen, for example in admixture with the peptide antigen or may be administered sequentially as a separate formulation.

Monoclonal antibodies may be prepared by any method known in the art such as the hybridoma technique (Kohler & Milstein, 1975, Nature, 256:495-497), the trioma technique, the human B-cell hybridoma technique (Kozbor et al., 1983, Immunology Today, 4:72) and the EBV-hybridoma technique (Cole et al., Monoclonal Antibodies and Cancer Therapy, pp 77-96, Alan R Liss, Inc., 1985).

Antibodies for use in the invention may also be generated using single lymphocyte antibody methods by cloning and expressing immunoglobulin variable region cDNAs generated from single lymphocytes selected for the production of specific antibodies by, for example, the methods described by Babcook, J. et al., 1996, Proc. Natl. Acad. Sci. USA 93(15):7843-78481; WO92/02551; WO2004/051268 and International Patent Application number WO2004/106377.

Screening for antibodies can be performed using assays to measure binding. An example of a binding assay is an ELISA, in particular, employing a conjungated secondary antibody to detect anti-ion channel antibody. An example of a blocking assay is a flow cytometry based assay where a fluorescently labelled secondary antibody is used to detect the amount of binding to the cell.

One aspect there is provided an antibody or fragment thereof identified employing the present method. The present invention also provides an isolated DNA sequence encoding the heavy and/or light chain(s) of an antibody molecule identified by a method of the present invention. Suitably, the DNA sequence encodes the heavy or the light chain of an antibody molecule of the present invention. The DNA sequence of the present invention may comprise synthetic DNA, for instance produced by chemical processing, cDNA, genomic DNA or any combination thereof.

DNA sequences which encode an antibody molecule of the present invention can be obtained by methods well known to those skilled in the art. For example, DNA sequences coding for part or all of the antibody heavy and light chains may be synthesised as desired from the determined DNA sequences or on the basis of the corresponding amino acid sequences.

DNA coding for acceptor framework sequences is widely available to those skilled in the art and can be readily synthesised on the basis of their known amino acid sequences.

In one embodiment the method comprises the further step of preparing DNA encoding an antibody or fragment according to the present disclosure.

Standard techniques of molecular biology may be used to prepare DNA sequences coding for the antibody molecule of the present invention. Desired DNA sequences may be synthesised completely or in part using oligonucleotide synthesis techniques. Site-directed mutagenesis and polymerase chain reaction (PCR) techniques may be used as appropriate.

The present invention also relates to a cloning or expression vector comprising one or more DNA sequences of the present invention. Accordingly, provided is a cloning or expression vector comprising one or more DNA sequences encoding an antibody of the present invention. Suitably, the cloning or expression vector comprises two DNA sequences, encoding the light chain and the heavy chain of the antibody molecule of the present invention, respectively.

In one example the vector comprises an intergenic sequence between the heavy and the light chains, such as IGS2 (see WO03/048208).

In one aspect the invention comprises the further step of preparing a cloning or expression containing said DNA.

General methods by which the vectors may be constructed, transfection methods and culture methods are well known to those skilled in the art. In this respect, reference is made to “Current Protocols in Molecular Biology”, 1999, F. M. Ausubel (ed), Wiley Interscience, New York and the Maniatis Manual produced by Cold Spring Harbor Publishing.

Also provided is a host cell comprising one or more cloning or expression vectors comprising one or more DNA sequences encoding an antibody of the present invention. Any suitable host cell/vector system may be used for expression of the DNA sequences encoding the antibody molecule of the present invention. Bacterial, for example E. coli, and other microbial systems may be used or eukaryotic, for example mammalian, host cell expression systems may also be used. Suitable mammalian host cells include CHO, myeloma or hybridoma cells.

Thus in one embodiment the method of the present disclosure comprises the step of preparing a suitable host for expressing antibody or fragment as described herein.

The present invention also provides a process for the production of an antibody molecule according to the present invention comprising culturing a host cell containing a vector of the present invention under conditions suitable for leading to expression of protein from DNA encoding the antibody molecule of the present invention, and isolating the antibody molecule.

The antibody molecule may comprise only a heavy or light chain polypeptide, in which case only a heavy chain or light chain polypeptide coding sequence needs to be used to transfect the host cells. For production of products comprising both heavy and light chains, the cell line may be transfected with two vectors, a first vector encoding a light chain polypeptide and a second vector encoding a heavy chain polypeptide. Alternatively, a single vector may be used, the vector including sequences encoding light chain and heavy chain polypeptides.

The antibodies and fragments according to the present disclosure are expressed at good levels from host cells. Thus the properties of the antibodies and/or fragments are optimised and condusive to commercial processing.

In one embodiment the method comprises the further step of preparing a humanized or chimeric antibody.

Humanised antibodies (which include CDR-grafted antibodies) are antibody molecules having one or more complementarity determining regions (CDRs) from a non-human species and a framework region from a human immunoglobulin molecule (see, e.g. U.S. Pat. No. 5,585,089; WO91/09967). It will be appreciated that it may only be necessary to transfer the specificity determining residues of the CDRs rather than the entire CDR (see for example, Kashmiri et al., 2005, Methods, 36, 25-34). Humanised antibodies may optionally further comprise one or more framework residues derived from the non-human species from which the CDRs were derived.

Chimeric antibodies are composed of elements derived from two different species such that the elements retain the characteristics of the species from which it is derived. Generally a chimeric antibody will comprise a variable region from one species, for example a mouse, rat, rabbit or similar and constant region from another species such as a human.

When the CDRs are grafted, any appropriate acceptor variable region framework sequence may be used having regard to the class/type of the donor antibody from which the CDRs are derived, including rat, rabbit, mouse, primate and human framework regions. Preferably, the CDR-grafted antibody of the present invention has a variable domain comprising human acceptor framework regions as well as one or more of the CDRs derived from the donor antibody as referred to herein. Thus, provided is a CDR-grafted antibody wherein the variable domain comprises human acceptor framework regions and non-human, preferably rat, mouse or rabbit donor CDRs.

Examples of human frameworks which can be used in the present invention are KOL, NEWM, REI, EU, TUR, TEI, LAY and POM (Kabat et al., supra). For example, KOL and NEWM can be used for the heavy chain, REI can be used for the light chain and EU, LAY and POM can be used for both the heavy chain and the light chain. Alternatively, human germline sequences may be used; these are available at: vbase.mrc-cpe.cam.ac.uk/. In a further alternative a database of affinity matured human V region sequences may be used as a framework.

In a CDR-grafted antibody of the present invention, the acceptor heavy and light chains do not necessarily need to be derived from the same antibody and may, if desired, comprise composite chains having framework regions derived from different chains.

Also, in a CDR-grafted antibody of the present invention, the framework regions need not have exactly the same sequence as those of the acceptor antibody. For instance, unusual residues may be changed to more frequently-occurring residues for that acceptor chain class or type. Alternatively, selected residues in the acceptor framework regions may be changed so that they correspond to the residue found at the same position in the donor antibody (see Reichmann et al., 1998, Nature, 332, 323-324). Such changes should be kept to the minimum necessary to recover the affinity of the donor antibody. A protocol for selecting residues in the acceptor framework regions which may need to be changed is set forth in WO 91/09967.

Donor residues are residues from the donor antibody, i.e. the antibody from which the CDRs were originally derived, which may in one embodiment of the present invention be either of the rat, mouse or rabbit antibodies may be incorporated into the final antibody or fragment as required.

In one embodiment, the antibody, or fragment such as a Fab or Fab′ fragment is a monoclonal, fully human, humanized or chimeric antibody fragment. In one embodiment the antibody Fab or Fab′ fragments are fully human or humanised.

Antibodies for use in the present invention include whole antibodies of any suitable class for example, IgA, IgD, IgE, IgG or IgM or subclass such as IgG1, IgG2, IgG3 or IgG4, and functionally active fragments or derivatives thereof and may be, but are not limited to, monoclonal, humanised, fully human or chimeric antibodies.

Antibodies for use in the present invention may therefore comprise a complete antibody molecule having full length heavy and light chains or a fragment thereof and may be, but are not limited to Fab, modified Fab, Fab′, F(ab′)₂, Fv, single domain antibodies (such as VH, VL, VHH, IgNAR V domains), scFv, bi, tri or tetra-valent antibodies, Bis-scFv, diabodies, triabodies, tetrabodies and epitope-binding fragments of any of the above (see for example Holliger and Hudson, 2005, Nature Biotech. 23(9):1126-1136; Adair and Lawson, 2005, Drug Design Reviews-Online 2(3), 209-217). The methods for creating and manufacturing these antibody fragments are well known in the art (see for example Verma et al., 1998, Journal of Immunological Methods, 216, 165-181). Other antibody fragments for use in the present invention include the Fab and Fab′ fragments described in International patent applications WO2005/003169, WO2005/003170 and WO2005/003171. Multi-valent antibodies may comprise multiple specificities or may be monospecific (see for example WO 92/22853 and WO05/113605).

In one example the antibodies for use in the present invention may be derived from a camelid, such as a camel or llama. Camelids possess a functional class of antibodies devoid of light chains, referred to as heavy chain antibodies (Hamers et al., 1993, Nature, 363, 446-448; Muyldermans, et al., 2001, Trends. Biochem. Sci. 26, 230-235). The antigen-combining site of these heavy-chain antibodies is limited to only three hypervariable loops (H1-H3) provided by the N-terminal variable domain (VHH). The first crystal structures of VHHs revealed that the H1 and H2 loops are not restricted to the known canonical structure classes defined for conventional antibodies (Decanniere, et al., 2000, J. Mol. Biol, 300, 83-91). The H3 loops of VHHs are on average longer than those of conventional antibodies (Nguyen et al., 2001, Adv. Immunol., 79, 261-296). A large fraction of dromedary heavy chain antibodies have a preference for binding into active sites of enzymes against which they are raised (Lauwereys et al., 1998, EMBO J, 17, 3512-3520). In one case, the H3 loop was shown to protrude from the remaining paratope and insert in the active site of the hen egg white lysozyme (Desmyter et al., 1996, Nat. Struct. Biol. 3, 803-811 and De Genst et al., 2006, PNAS, 103, 12, 4586-4591 and WO97049805).

It has been suggested that these loops can be displayed in other scaffolds and CDR libraries produced in those scaffolds (See for example WO03050531 and WO97049805).

In one example the antibodies for use in the present invention may be derived from a cartilaginous fish, such as a shark. Cartilaginous fish (sharks, skates, rays and chimeras) possess an atypical immunoglobulin isotype known as IgNAR. IgNAR is an H-chain homodimer that does not associate with light chain. Each H chain has one variable and five constant domains. IgNAR V domains (or V-NAR domains) carry a number of non canonical cysteines that enable classification into two closely related subtypes, I and II. Type II V regions have an additional cysteine in CDRs 1 and 3 which have been proposed to form a domain-constraining disulphide bond, akin to those observed in camelid VHH domains. The CDR3 would then adopt a more extended conformation and protrude from the antibody framework akin to the camelid VHH. Indeed, like the VHH domains described above, certain IgNAR CDR3 residues have also been demonstrated to be capable of binding in the hen egg white lysozyme active site (Stanfield et al., 2004, Science, 305, 1770-1773.

Examples of methods of producing VHH and IgNAR V domains are described in for example, Lauwereys et al, 1998, EMBO J. 1998, 17(13), 3512-20; Liu et al., 2007, BMC Biotechnol., 7, 78; Saerens et al., 2004, J. Biol. Chem., 279 (5), 51965-72.

In one embodiment the constant region employed, in the antibody or certain fragments thereof according to the disclosure, is a hybrid constant region or mutated constant region. Hybrid constant regions comprises portions or domains from two or more distinct constant regions, for example two or more distinct human constant regions.

Examples of hybrid constant regions include those disclosed in U.S. 2007/0041972, where at least CH1 and the hinge region are derived from one or more IgG2 antibodies and at least a portion of the CH2 and CH3 regions are derived from one or more IgG4 CH2 and CH3 regions. Eculizimumab (Alexion Pharmaceuticals) is a humanised anti-human C5 mAb for paroxysmal nocturnal hemoglobinuria comprising a hybrid constant region. It has a hybrid chain of IgG2 derived CH1 and hinge with IgG4 derived CH2 and CH3 domains. It does not bind FcγR nor does it activate complement. It also has low immunogenicity (low titres of anti-Eculizimumab antibodies detected in only 3 of 196 (3%) patients).

WO 2008/090958 discloses certain hybrid constant regions comprising a chain of CH1, hinge and CH2 from IgG1 and a CH3 domain from IgG3. The hybrid has a higher CDC activity than that of an IgG1 or IgG3 antibody and a protein A-binding activity equivalent to that of IgG1.

Further hybrid constant regions are disclosed in Tao et al., (S. L. Morrison's group) J. Exp. Med 173 1025-1028, 1991. This paper contains many IgG domain swaps from all classes but the key hybrids are g1g4 and g4g1, each joined in the CH2 domain.

IgG (1-1-1/4-4) is completely unable to activate complement in contrast to IgG1. However, IgG(4-4-4/1-1) showed significant activity compared with IgG4 but was slightly impaired compared with IgG1. The key difference seems to be the hinge and many papers have since demonstrated that the hinge modulates but does not mediates complement activation.

Tao et al., (S. L. Morrison's group) J. Exp. Med 178 661-667, 1993 discloses structural features of human IgG that determine isotype-specific differences in complement activation. Ser331 (CH2) in IgG4 prevents C1q binding and complement activation. Mutagenesis of Ser331 to Pro in IgG4 and IgG (1-1-1/4-4) allows binding and activation but at a lower level than that of IgG1. Interestingly P331S in IgG1 allows binding but not activation.

Zucker et al., Canc Res 58 3905-3908 1998 employs Chimeric human-mouse IgG abs with shuffled constant region exons to demonstrate that multiple domains contribute to in vivo half-life. In particular this article examines half-life of IgG (1-1-1/4-4) hybrid and others. In SCID mice, IgG (1-1-1/4-4) has a significantly longer half-life than IgG4 but slightly less than IgG1. IgG (4-4-4/1-1) has the longest half-life.

An example of a mutated constant region includes that employed in Abatacept, which is a fusion of human CTLA-4 with IgG1 hinge-Fc. The hinge was altered from CPPC to SPPS. The latter is O-gly. The mutated constant region does not mediate ADCC or CDC and has low immunogenicity (3% incidence).

The hinge is thought to potentially have a role in complement activation. The functional hinge, deduced from crystallographic studies, extends from 216-237 of IgG1 and consists of EPKSCDKTHTCPPCPAPELLGG (SEQ ID NO: 70) upper, middle and lower hinge respectively. In one embodiment an antibody or fragment according to the disclosure comprises a functional hinge.

Mutations/modifications to the constant region may, for example result in increased stability, for example U.S. 2004/0191265 discloses mutagenesis of IgG1 hinge, which increased the stability of an IgG by introducing one or more amino acid modifications in the hinge region at positions 233-239 or 249 of human IgG1. This provided reduced degradation upon heating to 55° C. for one week.

Alternatively, modification may be effected by making point mutations in labile amino acids (e.g., histidine or threonine) or reactive amino acids (e.g., lysine or glutamic acid) in the upper hinge portion (human IgG1 residues 226-243 and corresponding residues in other IgG subtypes and/or immunoglobulins from other species) and/or in the flanking CH1 and/or CH2 sequences (human IgG1 residue 249 and corresponding residues in other IgG subtypes and/or immunoglobulins from other species).

In further aspect there is provided a composition comprising an ion channel extracellular peptide for immunizing a host.

EXAMPLES Therapeutic Antibody Generation/Selection

Peptides were supplied by Peptide Protein Research Ltd., Fareham, U. K. N to C terminal cyclic peptides were synthesised as side chain protected peptides according to the method of Barbs et al Int. J. Pept. Protein Res. 1991 and cyclisation was carried out in solution phase followed by side chain deprotection according to the method of Kessler H et al., 1989, in Computer-aided drug design, methods and applications, Ed. T. J. Perun and C. L. Probst, pp. 461-484, Marcel Dekker, New-York; Toniolo C., 1990, Int. J. Pept. Protein Res., 35, 287-300; Gurrath M. et al., 1992, Eur. J. Biochem., 210, 911-921; Izumiya N. et al., 1981, Biopolymers, 20, 1785-1791; Brady S. F. et al., 1983, in Peptides, Structure and Function, Proceedings of the Eighth American Peptide Symposium, Ed. V. J. Hruby and D. H. Rick, pp. 127-130, Pierce Chemical Company, Rockford, Ill.; He J. X. et al., 1994, Lett. Peptide Sci., 1, 25-30. Rabbits were immunised with combinations of human Na_(v)1.7 peptides conjugated to either KLH, OVA or BSA (Table 1). Following 5 subcutaneous immunisations (KLH, OVA, BSA, KLH, OVA), animals were sacrificed and PBMC, spleen and bone marrow harvested. Sera was tested for binding to human biotinylated peptide in ELISA.

TABLE 1 Rabbit Peptides Peptide Sequence 3822 A32 A32-CTLESIMNTLESEEDFRKY (cyclic) (SEQ ID NO: 87) 3823 and B11, B31 B11-CPMTEEFKN (cyclic) 3824 (SEQ ID NO: 90) B31-CTLPRWHMNDD (cyclic) (SEQ ID NO: 102) 5825 C11 C11-CIERKKTIKI (cyclic) (SEQ ID NO: 92) Table 1. Na_(v)1.7 Peptide Immunogens

The table shows immunised rabbit number, peptide combination employed for immunisation and peptide sequence. A32 is a peptide from loop E3 in domain A. B11 is a peptide from loop E1 in domain B. B31 is a peptide from loop E3 in domain B. C11 is a peptide from loop E1 in domain C.

SLAM was performed using substantially the methods described in Tickle et al. 2009 (JALA, Vol. 14, number 5, p 303-307). Briefly, SLAM cultures were set up using rabbit splenocytes or PBMC and supernatants were first screened for their ability to bind biotinylated peptide in a bead-based assay in the FMAT. This was a homogeneous assay using biotinylated human peptide bound to streptavidin beads (Bangs Laboratories) and revealing binding using a goat anti-rabbit Fc-Cy5 conjugate (Jackson immunoResearch). Positives from this screen were then put through a negative screen to identify non-specific antibodies. This used streptavidin beads with no peptide or with an irrelevant peptide, revealing binding with a goat anti-rabbit Fc-Cy5 conjugate (Jackson ImmunoResearch), to identify the peptide specific binders.

From 10 SLAM experiments, a number of A-32-specific, B11-specific and C, 11-specific antibody-containing wells were identified using the screens described above. Single B cell isolation via the fluorescent foci method and subsequent variable region gene cloning from a number of these wells successfully yielded heavy and light chain variable region gene pairs following reverse transcription (RT)-PCR. These V-region genes were cloned as rabbit IgG1 full-length antibodies and re-expressed in a HEK-293 transient expression system.

Sequence analysis of cloned v-regions revealed the presence of a number of unique families of anti-human B11-specific Na_(v)1.7 antibody and A32-specific antibodies (see table 2 below). DNA and amino acid sequences of these antibodies are shown in the Figures. Antibodies were expressed in a transient CHO system and subsequently purified to allow further characterisation in vitro and in vivo.

TABLE 2 UCB antibody Rabbit Peptide number number specificity CA167_00915 3822 A32 CA167_00914 3822 A32 CA167_00933 3822 A32 CA167_00932 3822 A32 CA167_00931 3822 A32 CA167_00930 3822 A32 CA167_00983 3824 B11 CA167_00984 3824 B11 CA167_00985 3824 B11 CA167_01080 3824 B11 CA167_01081 3824 B11 CA167_01082 3824 B11 CA167_01083 3824 B11 CA167_01084 3824 B11 CA167_01085 3824 B11 CA167_01086 3824 B11

FIGS. 6-11 show sequences for anti-Na_(v)1.7 antibodies. The immunised rabbit number that the antibodies were derived from and their peptide specificities are detailed.

Procedure for h Na_(v)1.7 Recording for Antibody Testing

Solutions and Antibodies Handling

Extracellular solution contained (in mM): 130 NaCl, 4 KCl, 1.5 CaCl₂, 1 MgCl₂, 30 glucose, 10 HEPES (pH 7.4 with Tris-Base, and 300 to 305 mOsmolar). Intracellular solution contained (in mM): 5 NaCl, 115 CsF, 20 CsCl, 110 HEPES, 10 EGTA free acid (pH 7.2 with CsOH, and 290 to 295 mOsmolar) and was either made fresh or kept frozen. Extracellular and intracellular solutions were filtered prior to use. Antibodies were directly diluted in extracellular solution and were freshly (no more than 15 min) prepared before transfer to a 96-well polypropylene compound plate (Sarsted, #83.1835.500). For the experiments using selective peptide, antibodies and peptides, at equal concentrations, were preincubated at least 30-min at 4° C. prior Patch Clamp experiments.

Cell Preparation

HEK293 cells stably expressing the human Na_(v)1.7 channel (type IX voltage-gated sodium channel alpha subunit) were purchased from Upstate (Upstate, Millipore, cat.#CYL3011). Cells were cultured in T-75 (BD BioCoat™ Collagen I Cellware, Becton Dickinson Labware, Bedford, Mass., #356485) flasks coated with collagen type I using standard culture medium DMEM-F12 with-Glutamine (Invitrogen, #11320) containing 10% FBS (Lonza, #DE14-802F), 1% penicillin+streptomycin (Lonza, DE17-603E), 1% non essential amino acids (Lonza, BE13-114E) and 400 μg/ml G418 (GIBCO, #10131-027). Cells were plated at a density of 15,000 cells/cm2 or 8,000 cells/cm2 density for 2 or 3 days respectively before being used on PatchXpress® 7000A (Axon instrument, new part of MDS Analytical Technologies). Cells confluence never exceeded 90%. The day of the experiment, cells were harvested using Accumax (Sigma, A7089). Briefly, cells were washed twice in PBS (Lonza, #BE12-516F) without calcium and magnesium, and a 1:4 dilution of Accumax solution was added and incubated for 1.5 to 2-min at 37° C. DMEM-F12 with 15 mMHEPES and L-glutamine (Lonza, #BE12-719F) containing 10% FBS (recovery media) was added to quench Accumax digestion. The cells were subsequently centrifuged at 1,000 rpm for 5-min in 50 ml falcon tube and pellets are resuspended in 10 ml of recovery media. Cells are counted (CoulterZ2) and suspended at ˜0.1 million cells/ml and transferred to a 15 ml screw-cap tube for minimum 90 minutes at room temperature. Cells were then centrifuged for 60-s at 1,000 rpm. The pellet was gently resuspended in 1,000 μl extracellular solution and centrifuged a second time for 30-s at 1,000 rpm. Pellet was resuspended in 150 μL extracellular solution and immediately tested on the PatchXpress®.

PatchXpress® Procedures

The AVIVA Biosciences SealChip16™ electrode arrays (purchased from Axon Instruments, Union City, Calif.) were manually placed in the holder of the PatchXpress® system and automatically prepared for application of the cells. Intracellular solution was injected into the bottom of each chamber, and extracellular solution was perfused into the top of the chambers through the 16-nozzle wash station. Throughout this period, the pressure controller maintained a positive pressure (+10 mmHg) from the intracellular side to keep the hole free of debris. Cells were triturated by the integrated Cavro pipetting robot prior to addition of 4 μl (containing 10K-30K cells) to each well.

PatchXpress® h Na_(v)1.7 Assay

After 10-s, the pressure was switched from +4 to −30 mmHg to attract suspended cells to each of the 16 holes (electrodes). Seal formation was achieved by repeating negative pressure ramp from −1 to −35 mmHg at a rate of 1.6 mmHg/s every 36-s until a Giga Ohm Seal was obtained and verified for 20-s. Whole-cell access was achieved by rupturing the patch of membrane over the hole using a ramp increase in negative pressure from −40 to −150 mmHg at a rate of 7.5 mmHg/s with a pipette potential of −80 mV. After whole cell configuration cells are washed with extracellular solution for 66-s to remove the excess cells in the well. The cell was allowed to dialyze for 5 min, during which the access resistance was monitored. From the time of whole-cell break-in to the end of the experiment, the cells were held at −80 mV between voltage protocols. A time course protocol was applied to assess the antibody potencies on sodium current elicited by a depolarizing step from −80 mV to 0 mV for 20 milliseconds at 10 seconds interval. Whole cell compensation was automatically made before each trial starts and electrical access resistance (Ra) was corrected by 65%. Linear leak substraction was performed online using a P/N leak subtraction protocol (N=4) at the holding of −80 mV.

After a stabilizing period (up to 10 min), a negative control solution (extracellular solution) was applied for 5-min, followed by two doses of antibodies. The interval between both additions of the same concentration of compound to a well was ˜11-s. Antibody solution (45 μL) was added online (30 μL/s) at the desired concentration with permanent aspiration. Currents were monitored continuously during the 18-min exposure to the antibody.

Data Analysis

-   Cells were not analyzed if:

(1) the membrane resistance was initially <200 MOhm,

-   -   (2) current amplitude <200 pA,     -   (3) an access resistance no greater then 20 MOhm and     -   (4) no real stabilized current after negative control addition.

The current amplitude was measured using DataXpress2 software (Axon instruments) and rundown current correction was performed by linear or exponential fitting method on the measurement associated with the last 10-15 data points after the washout period and the last 10-15 data point after the negative control addition.

Current was normalized by the mean current corrected amplitude prior antibody addition.

Current inhibition was estimated by the residual response after 18-min antibodies application.

Data is given below in Table 3.

TABLE 3 Table 3: Inhibition of Nav 1.7 currents expressed in HEK cells. Concentration Antibody Peptide (μg/ml) Nav1.7 inhibition (%) CA167_00914 A32 25 28 CA167_00915 A32 25 26 CA167_00931 A32 2.5 9 CA167_00932 A32 25 27 CA167_00933 A32 25 8 CA167_00983 B11 25 41 CA167_00984 B11 25 9 CA167_00985 B11 25 12 CA167_01080 B11 25 46 CA167_01081 B11 25 33 CA167_01082 B11 25 10 CA167_01083 B11 25 16 CA167_01084 B11 25 27 CA167_01085 B11 25 27 CA167_01086 B11 25 31 R3822_A32 A32 25 53 R3824_B11 B11 25 68 R5825_C11 C11 25 20 FIG. 2

FIG. 2 shows the functional effects of selected antibodies (at 25 μg/ml), in the presence or absence of specific peptide, on human Nav1.7 currents expressed in HEK cells. Nav1.7 currents were recorded by automated Patch Clamp using a repetitive stimulation protocol and data are presented as the normalized Nav1.7 current after the last stimulation. Selected antibodies were incubated in the presence of the specific peptide (25 μg/ml) for 30 minutes at 4° C. and then transferred to the PatchXpress system for Nav1.7 current recordings. The presence of the peptide systematically reverses the inhibitory effect of the antibody thus indicating that inhibition of Nav1.7 currents is mediated by a specific interaction of antibodies with the Nav1.7 extracellular loops.

FIG. 3 e (a)

Automated Patch Clamp analysis of recombinant human Nav1.7 channels expressed in HEK cells. 983 monoclonal antibody produces a dose-dependent inhibition of Nav1.7 currents. Data points represent the normalized peak current amplitudes after application of a repeated voltage step protocol (end point) in the presence of antibody.

FIG. 3 e (b)

Automated Patch Clamp analysis of recombinant human Nav1.7 channels expressed in HEK cells. 1080 monoclonal antibody produces a dose-dependent inhibition of Nav1.7 currents. Data points represent the normalized peak current amplitudes after application of a repeated voltage step protocol (end point) in the presence of antibody.

FIG. 3 f

Automated Patch Clamp analysis of recombinant rat Nav1.7 channels expressed in HEK cells. 983 monoclonal antibody produces a dose-dependent inhibition of Nav1.7 currents. 1080 monoclonal antibody produces a ˜26% inhibition of Nav1.7 currents at 25 μg/ml. Data points represent the normalized peak current amplitudes after application of a repeated voltage step protocol (end point) in the presence of antibody.

FIG. 3 g

Kinetics of human Nav1.7 inhibition by 983 monoclonal antibody. HEK cells expressing recombinant human Nav1.7 channels are stimulated with a voltage step protocol at 0.1 Hz for ˜20 minutes. Data points represent the normalized peak current amplitudes (run down corrected) of Nav1.7 channels recorded every 10 seconds. Nav1.7 currents are reduced in the presence of the antibody (25 μg/ml) but only when repeated activation of the channel at 0.1 Hz is maintained. Stimulation of Nav1.7 channels only at the end of the protocol (and after incubation of antibody) does not produce an inhibition of the Nav1.7 current. Data suggest that specific inhibition by 983 monoclonal antibody requires repetitive activation (channel cycling) of the Nav1.7 channel protein.

Dorsal Route Ganglion in vitro Testing

Primary Culture Preparation

Dorsal Root Ganglia were isolated from 1-2 wild-type rat pups, aged between postnatal day 1 and 3. Ganglia were washed in PBS after dissection and immediately placed into a DMEM (Lonza, #BE12-604F) solution containing 2 mg/ml collagenase (Sigma-Aldrich, #C2674) and incubated at 37° C. for approximately 45 minutes for enzymatic digestion. Collagenase solution was removed and replaced with DMEM supplemented with 10% Fetal Bovine Serum (Lonza, #DE14802F), 0.5 mM L-Glutamine (Lonza, #BE17-605E), 1% Penicillin/Streptomycin (Lonza, #BE17-603E) and 20 ng/ml nerve growth factor (NGF, Invitrogen). Ganglia were then mechanically triturated, centrifuged at 1000 g for 5 minutes, and resuspended in the same culture medium. Dissociated cells were counted and diluted to a suspension of 100,000-120,000 cells/ml on glass coverslips precoated with 50 μg/ml poly-D-lysine (Sigma) and 30 μg/ml laminin (Invitrogen) and incubated at 37° C., 5% CO₂ until ready for use.

Primary Culture Electrophysiology

Dissociated DRG were taken for use no more than two days in vitro (DIV) following preparation. Cells were visualized on an Olympus BX50WI upright microscope with an Ikegami ICD-42B CCD camera. Electrophysiological recordings were acquired using 5 khz digital sampling and filtered at 3 dB at a 3 khz frequency on an Axopatch 1D (Molecular Devices) amplifier and converted to a digital signal using a Digidata 1322A analog-to-digital converter (Molecular Devices). All recordings were acquired using pClamp 10 software (Molecular Devices) and subsequently analyzed in Clampfit 10 (Molecular Devices). Recording electrodes were pulled from borosilicate glass pipettes on a Sutter p-97 horizontal pipette puller to a final resistance of 4.5-6MΩ and filled with an internal solution containing (in mM): 140 K-Methansulfonate, 5 NaCl, 1 CaCl2, 2 MgCl2, 11 EGTA, 10 HEPES, 2 Mg-ATP, and 1 Li-GTP; pH was adjusted to 7.2 with Tris-base, and osmolality was adjusted to 310 mOsm with sucrose. Bath solution contained (in mM): 130 NaCl, 25 glucose, 10 HEPES, 4 KCl, 2 CaCl₂, 1 MgCl₂, 1.25 NaPO₄; pH was adjusted to 7.35 with NaOH and osmolality was adjusted to 310 mOsm with sucrose. The liquid junction potential was calculated to be 14.2 mV, all reported voltages have been corrected to compensate.

After formation of a tight seal (>1 GΩ) by release of positive pressure and manual suction in voltage clamp mode, capacitative currents were compensated and the command voltage was set to −70 mV. The cell membrane was ruptured and the cell allowed to dialyze intracellular solution for 5 minutes. Whole cell parameters were recorded after dialysis. Cells were rejected if whole cell capacitance was >35 pF or a stable access resistance less than 3× electrode resistance could not be achieved. The amplifier was switched to current clamp mode and the resting membrane potential was recorded. The cell was then injected with a series of 1.5 s duration, depolarizing current steps of increasing amplitude intended to evoke an action potential (AP) or train of APs. Cells that could not fire more than a single AP during a single step after depolarizing to a maximum of −35 mV were rejected.

Cells were subsequently treated either with control or antibody solutions by fast bath perfusion directly on to the recorded cell for 90 seconds to sufficiently fill the recording chamber, at which point both perfusion and aspiration were halted. The previous series of depolarizing current steps were repeatedly administered at two minute intervals over a period of 40 minutes, typically with a delay of 1.5 s between individual steps to allow for membrane repolarization. Occasionally a constant current was injected if the resting membrane potential (RMP) adjusted over the course of the experiment in order to maintain a constant RMP of −65 mV. Cells whose RMP deviated more than 20% in either the positive or negative direction or whose holding current changed more than 100 pA during the course of the experiment were rejected. Individual holding currents and injected currents for each step were noted individually for each cell, as well as any electrophysiological parameters that were changed during the course of the experiment.

Data Analysis

Action Potentials (AP) were manually counted for each depolarizing step and the total number of evoked APs were summed for each time point. The number of APs at each time point were normalized in Microsoft Excel 2003 to the number of evoked APs at time=0 and plotted as a function of time using Graphpad Prism 5.0 software. Each plotted data point represents the mean value of all recorded cells under the specified experimental condition, with error bars representing the calculated standard error.

FIG. 3 a Current clamp traces of evoked action potentials from representative DRG neurons before (time=0) and following (time=30 minutes) treatment.

FIG. 3 b The antibody 932 (25 μg/ml) significantly reduced the number of evoked action potentials compared with vehicle or control antibody treated controls following antibody administration at time=2 minutes.

FIG. 3 c: The antibody 983 (25 μg/ml) significantly reduced the number of evoked action potentials compared with vehicle or control antibody treated controls following antibody administration at time=2 minutes.

FIG. 3 d

Electrophysiology (current clamp recordings) investigations on action potential firing in cultured rat dorsal root ganglion (DRG) neurons. 1080 monoclonal antibody, at a dose of 25 μg/ml, reduces the electrically induced spike frequency of DRG neurons. Data points represent the normalized spike frequency compared to initial frequency observed at time 0 before antibody application.

Isoform and Species Selectivity for 983 and 1080

TABLE 4 E1 peptides used for Nav isoform and species selectivity studies Peptide Name Ion channel Sequence B11.1 Nav 1.1 Cyclo[biotinyl-PEG-cysEHYPMTDHFNN] (SEQ ID NO: 159) B11.2/3 Nav 1.2 and 1.3 Cyclo[biotinyl-PEG-cysEHYPMTEQFSS] (SEQ ID NO: 160) B11.4 Nav 1.4 Cyclo[biotinyl-PEG-cysEHYPMTEHFDN] (SEQ ID NO: 161) B11.5 Nav 1.5 Cyclo[biotinyl-PEG-cysEHYNMTSEFEE] (SEQ ID NO: 162) B11.6 Nav 1.6 Cyclo[biotinyl-PEG-cysEHHPMTPQFEH] (SEQ ID NO: 163) B11.7 Nav 1.7 Cyclo[biotinyl-PEG-cysPMTEEFKN] (SEQ ID NO: 90) B11.8 Nav 1.8 Cyclo[biotinyl-PEG-cysEHHGMSPTFEA] (SEQ ID NO: 164) B11.9 Nav 1.9 Cyclo[biotinyl-PEG-cysEHHKMEASFEK] (SEQ ID NO: 165) Peptide Binding ELISA

Nunc 96 well plates were coated overnight 4° C. in 5 ug/ml Streptavidin (Jackson 016-000-114) 100 ul/well in carbonate coating buffer. Plates were washed four times in PBS/tween and 200 ul/well of block (1% BSA in PBS) was added for 1 hour at RT.

Plates were washed four times in PBS/tween and 100 ul/well of biotinylated peptide at 5 ug/ml was added for 1 hour at RT. Plates were washed four times in PBS/tween and 100 ul/well of antibody added (starting at 10 ug/ml diluting in block in half logs down the plate) for 1 hour at RT. Plates were washed four times in PBS/tween and 100 ul/ml goat anti rabbit Fc HRP (Jackson 111-036-046) added for 1 hour at RT. Plates were washed four times in PBS/tween and 100 ul/well TMB (3,3′,5,5′ Tetramethylbenzidine) solution added. 50 ul/well of NaF was added to stop reaction and absorbance read at 630 nm.

FIG. 4 shows ELISA data for antibody 983 binding to various cyclic Nav ion channel peptides Table 4

FIG. 5 shows ELISA data for antibody 1080 binding to various cyclic Nav ion channel peptides Table 4.

Specific binding in both cases was only observed for the B11.7 peptide and no binding to equivalent loops from the other Nav ion channels was observed.

Polyclonal Anti-Na_(v)1.7 Antibodies

Polyclonal anti-Na_(v)1.7 antibodies were raised against cyclic peptides A32 (SEQ ID NO:87), B11 (SEQ ID NO:90) and C11 (SEQ ID NO:92) using the immunization and SLAM screening methods described above prior to single B cell isolation via the fluorescent foci method and subsequent variable region gene cloning.

The polyclonal antibodies were purified as follows:

Biotinylated peptide, corresponding to the peptide conjugate used for immunization, was added to a final concentration of 10 μM peptide to diluted immune rabbit plasma harvested as a total bleed from the respective rabbit. The mixture was allowed to equilibrate at 4° C. for two days. Antibody peptide complexes were isolated by applying the plasma mixture to a streptavidin affinity column (HiTrap NHS ester column that had previously coupled with streptavidin).

After washing the column with 12 column volumes of phosphate buffered saline, anti-peptide antibody was eluted with 25 mM glycine/HCl pH 1.5 (3×20 ml fractions) and collecting each fraction into 5 ml 2M TRIS/EDTA pH 8.5. A second purification involved loading the neutralized fractions onto a HiTrap Protein G column followed by a 10 column volume phosphate buffered saline wash. Antibody was eluted with 20 column volumes of 0.1M glycine/HCl pH 2.7 and neutralizing fractions with 2M TRIS/EDTA pH 8.5. The latter were concentrated and using an Amicon Ultra 15 spin filter (50 kDa cut-off) then buffer exchanged into ‘patch Clamp buffer’ (10 mM HEPES, 130 mM NaCl, 4 mM KCl, 1.5 mM CaCl₂, 1 mM MgCl₂, 30 mM glucose pH 7.4). The resulting anti-peptide IgG was sterile filtered and protein concentration estimated by measuring absorbance at A_(280nm).

FIG. 12 shows binding data for affinity purified anti-Na_(v)1.7 polyclonal antibodies generated as described above. 

I claim:
 1. A method for generating an antibody to a potassium ion channel having a function in the modulation of pain comprising immunizing a host with a cyclic peptide comprising at least part of an extracellular sequence of said ion channel, wherein the extracellular sequence of said ion channel is an E1 extracellular region or E3 extracellular region, and the cyclic peptide comprises between 5 and 30 amino acids from said extracellular region.
 2. A method according to claim 1, wherein the potassium ion channel is selected from the group consisting of K_(v) 2.1, K_(v) 2.2, K_(v) 7.x, Kv3.1 and Kv3.2.
 3. A method according to claim 2, wherein the ion channel is K_(v) 3.2 and the cyclic peptide has the amino acid sequence of SEQ ID NO: 104 or SEQ ID NO:
 105. 4. A method according to claim 1, wherein the cyclic peptide is conjugated to a carrier.
 5. A method according to claim 4, wherein the carrier is ovalbumin, bovine serum albumin, or keyhole limpet hemocyanin.
 6. A method according to any one of claim 1, 2 to 3, or 4, wherein the cyclic peptide is joined in a region of sequence overlap in the linear sequence.
 7. A method according to any one of claim 1, 2 to 3, or 4, wherein the peptide is cyclised by formation of an amide bond.
 8. A method according to any one of claim 1, 2 to 3, or 4, wherein the peptide is cyclised by formation of a disulfide bond.
 9. A method according to any one of claim 1, 2 to 3, or 4, wherein an adjuvant is employed administered concomitantly or sequentially with the cyclic peptide to stimulate an immune response thereto.
 10. A method according to claim 9, wherein the adjuvant is selected from Freud's complete or incomplete adjuvant, a formulation comprising a saponin and/or MPL and/or CPU.
 11. A method according to any one of claim 1, 2 to 3, or 4, wherein the host is immunized multiple times.
 12. A method according to claim 11, wherein the host is immunized twice or three times.
 13. A method according to claim 12, wherein the host is immunized at 1 to 4 weekly intervals after a first immunization.
 14. A method according to claim 11, wherein at least one immunization, subsequent to the first immunization, employs a cyclic peptide conjugated to a carrier that is different to the carrier conjugated to the cyclic peptide employed in the first immunization.
 15. A method according to claim 11, wherein each immunization, subsequent to the first immunization, employs a peptide that is different to the carrier conjugated to the peptide employed in the first immunization.
 16. A method according to any one of claims 1, 2 to 3, or 4, wherein a number of distinct ion channel peptides are employed in combinations, for example in admixture, for immunizing the host.
 17. A method according to any one of claims 1, 2 to 3, or 4, which comprises the further step of harvesting cells generating antibodies.
 18. A method according to any one of claims 1, 2 to 3, or 4, which comprises the further step of identifying cells that generate antibodies to the ion channel peptide or peptides.
 19. A method according to any one of claims 1, 2 to 3, or 4, which comprises the further step of cloning an anti-ion channel antibody. 